Dry weather prevails with cold low temperatures and patchy morning frost and fog. Gusty north to east winds expected on Monday.
Discussion
Sunday morning GOES-West satellite imagery illustrates mostly clear skies across interior northern California with the exception of some patchy fog developing in the southern Sacramento and northern San Joaquin valleys. Current temperatures are in the 20s to 40s across the mountains, foothills and Valley, valid at 230 AM PST.
The upper level pattern will feature troughing to the east with ridging off the West Coast over the next few days. This will allow for dry weather to prevail. Daytime high temperatures will be in the 50s to 60s in the Valley and foothills, with 30s to 50s in the mountains. Temperatures will be trending near to above normal at times this week.
Patchy frost and fog will be possible in the mornings each day as well. There is about a 45-65% probability of visibilities of 1/2 mile or less from Marysville southward this morning. Motorists should drive slow and use caution if patchy fog is encountered. Overnight/morning low temperatures for the Valley are forecast to be in the 30s for the next several days. Lows will be around the 30s to low 40s for the foothills, with teens to 30s in the mountains. Be sure to take the necessary precautions to protect pets, plants, and people!
Gusty north to east winds will develop, mainly on Monday where the National Blend of Models (NBM) suggests a 35-65% probability of 40 MPH gusts along and west of Interstate 5 in the Valley, and a 65-85% probability of 50 MPH gusts in the mountains and north- east oriented gaps and canyons. Winds will decrease on Tuesday, with occasionally breezy downslope flow in the mountains and foothills continuing in the evening through early morning periods through the rest of the week.
Extended Discussion (Thursday through Sunday)
Cluster analysis and ensemble guidance depict upper level ridging to be the primary synoptic feature across interior NorCal to start the extended forecast period, allowing for dry weather and above normal temperatures to prevail. Above normal temperatures continue through late week, before cooling to near normal over next weekend as upper level troughing deepens over the Western US. This trough may also bring some light shower chances to the mountains Friday night into Saturday. Overnight temperatures will continue to remain on the chilly side at times, with morning lows generally in the 30s in the Valley.
Occasionally breezy north to east flow will continue late next week as well, and then another round of gusty north to east winds may develop next weekend as an offshore flow regime sets up once again (there is still some uncertainty in the clusters however).
The National Blend of Models (NBM) currently projects a 50-70% probability of wind gusts of 40 mph or greater along and west of Interstate 5 in the Valley, and a 60-80% probability in the mountains and northeast wind-prone gaps and canyons, all of which are already being highlighted with a signature on the Extreme Forecast Index (EFI) for next weekend.